


Midnight sea

by ElleLouMay



Series: Under the sea [1]
Category: Supernatural
Genre: Alpha Castiel/Omega Dean Winchester, Alpha/Beta/Omega Dynamics, Bottom Dean Winchester, Creature Castiel (Supernatural), Double Penetration, Dubious Consent, Just Sex, Language Barrier, M/M, Mates, Octopus Castiel (Supernatural), Plot What Plot/Porn Without Plot, Tentacle Sex, Top Castiel (Supernatural)
Language: English
Status: Completed
Published: 2019-05-30
Updated: 2019-05-30
Packaged: 2020-03-29 13:23:39
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,220
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/19020808
Author URL: https://archiveofourown.org/users/ElleLouMay/pseuds/ElleLouMay
Summary: The ocean never truly sleeps and in the darkest of the deeps there lingers all of God's most secret creations.Fish that glow as bright as newly birthed stars, unnamed species yet to be discovered by man and beings that defy all human logic that call the coldest reaches of the sea their homes.Of course to those creatures it is humans that are the strange beings





	Midnight sea

 

𝔹𝕐 𝔼•𝕃•𝕄𝔸𝕐

#  𝕞𝕚𝕕𝕟𝕚𝕘𝕙𝕥 𝕤𝕖𝕒

 

* * *

 

Dean rolled on his diving suit and bent at the waist to check the pressure on the newly stocked oxygen he'd be using tonight - he always preferred to do his work at night with the inky waters swallowing him and not a soul to bother him as he plunged down deeper to explore the depths.

 

Stowing his mobile away in his empty cuby beneath the small ships rail Dean readied himself as he stepped up onto the side.

The waters were blissfully calm and reflected the sky above like a dark mirror, he'd never get over the allure the water held over him.

 

Working as a marine biologist was something that had always appealed more to his little brother but Dean  _ did _ love the field work.

Getting to explore the endless nooks and crannies below was a dream come true for someone like Dean who had a never-ending thirst for exploration.

 

Dean sealed his lips around his oxygen feed and secured his mask before turning so that his back faced the water and flipping off the side of the boat in a well practiced dive that never failed to send a thrill through him.

As he sank out of sight his stashed phone blared 'Holy diver' by Dio with the led screen displaying his little brother's caller ID.

 

#  †

 The ocean never truly sleeps and in the darkest of the deeps there lingers all of God's most secret creations.

Fish that glow as bright as newly birthed stars, unnamed species yet to be discovered by man and beings that defy all human logic that call the coldest reaches of the sea their homes.

 

Of course to those creatures it is humans that are the strange beings.

 

#  †

 

Castiel rose from the tunnel and bobbed his head out of the surface as he neared the water's edge in his kindom, seeing his siblings moving along the rough stone ahead of him he lost no time pulling himself out fully and following them through to the next chamber where the group was gathered to eat.

 

Anna turned to meet his eye with a kind smile, "Any plans for off duty tonight, little brother?"

 

"I bet it'll be the same as always," Gabe interjected as he fell back to slither besides them, "Staring at the jellyfish all night long."

 

Jellyfish were fascinating creatures, clear and brightly coloured with long appendages like those of his people but lacking the raised suckers.

They absolutely fascinated Castiel and he was often found lurking where they frequented as he observed the gentle creatures.

 

"Leave him be, Gabe." Anna said as she whacked the back of their older brother's head with one of her orange tentacles.

 

Gabe just laughed and stuck his tongue out as they joined the rest of their siblings at the small dinner pit to eat their fill of the days catch.

 

#  †

 

Dean held onto the edge of a large, smooth, rock as he watched a swarm of jellyfish floating eerily along on a current.

They were beautiful in their ghostly glow as they trailed ribbons through the dark waters and he marvelled at them as they moved along, thoroughly entranced.

 

He was steadily lulled into a calm state as he moved onwards after the swarm dispersed to a level he deemed safe (jellyfish stings were a bitch) and continued to observe the mass of colour as it flowed before him - he often thought that watching the glowing life down in these deeps was what taking acid must be like, all swirling colours that bloomed bright.

 

Dean was drawn out of his trance when he noticed he wasn't getting any oxygen from his tank - looking back at his tank he could see a steady stream of bubbles erupting from his pack.

 

He'd never been in a situation like this before and although he knew he shouldn't panic it didn't stop his heart from jumping into his throat as he kicked his feet desperately trying to ascend back to the surface.

 

In his panic Dean accidentally brushed against a stray jellyfish that had escaped his line of sight and pain burst through his shoulder immediately causing him to gasp and let out a line of bubbles from his mouth as he continued kicking his legs.

 

#  †

 

 Castiel had never seen a creature like this one before - it was slim with thick muscles rippling beneath it's black skin and what appeared to be one, long, eye from this distance. It had a mass on it's back and four limbs, two ending in solid fins and the other two ending in what appeared to be small and pale tentacles.

It was the most amazing sight he'd ever laid eyes on and seemed to be hunting the jellyfish that were swimming in front of it.

 

As he watched bubbles started pouring from what Castiel had thought was the creature's back and he wondered if that's where it's gills were located or whether it had two mouths because it had been letting bubbles out from what he thought was a mouth at its front only moments before.

 

The creature seemed to get scared and Castiel watched as strong limbs beat the water fast and hard in a way he'd never seen before, the creature rose higher but a jellyfish had strayed from the group and Castiel winced as he witnessed the new creature getting stung - he knew from experience that it wasn't pleasant.

 

The creature let out a long stream of bubbles and then seemed to kick faster as it rose away from its attacker with renewed vigor.

Castiel moved to get a better look as the thing continued up at quite a speed and stared after it longingly as he wondered what the thing was.

 

#  †

 

A sharp ringing sound started in Dean's head as he fought against his burning lungs, trying to force them to not compulsively draw breath because there was  _ no _ way he was drowning tonight!

 

Darkness was ebbing at his peripheral and his arms and legs were tingling from the lack of oxygen and the strain of moving so hard and fast.

 

He couldn't be far from the surface now, surely he hadn't gone that deep?

 

The black of unconsciousness was pulling at his mind as his arms and legs got heavier...his mind buzzed and then blinked out as he was swallowed…

 

#  †

 

 The creature had stopped swimming so furiously and was now hovering with jerking limbs and a slow flow of bubbles still coursing from it's back.

Castiel moved closer to circle it and get a better look, he was concerned that the jellyfish sting had been somehow deadly to this new thing.

 

He moved in ever closer and once he drew level he could see two hazy, green, eyes beneath what he had thought was the thing's long eye. They looked the same size and shape as his own though the creature's were glossy and staring off at a spot just above Castiel's shoulder.

 

The thing was dying, he could see that now.

 

He had to help it but if he took it back...his kindom would kill it just because it was new.

 

#  †

 

 Dean's head swam as the world lurched around him and he sat too quickly in the dark, gulping in lungfuls of air stagnant tasting that made his lungs sear with agony like he was inhaling acid.

 

As his vision cleared some he looked around and found himself in a cave of some kind, the air was damp and stale as his eyes strained to see in the dim light cast by something that glowed white off to his side.

 

He turned his head and jerked back from the sight before him - a creature was watching him from a short distance with large, blue, eyes framed by thick lashes and set against an angular face with pale skin. His torso was bare and well defined descending in a hard line down to sharp hip bones that bled into a swirling mass of black/blue tentacles...actual  _ tentacles _ .

 

The creature was regarding him warily and clutching what appeared to be a roughly crafted spear with a jagged rock at the end tied by kelp.

 

It screeched out a hideous sound that made Dean slam his hands over his ears and screw his face up - he felt like his eardrums were rupturing.

 

"Stop! Stop it!" Dean shouted desperately.

 

Thankfully it stopped the painful sound and when Dean opened his eyes and uncovered his ears he saw the creature staring at him with a tilted head and brows furrowed in confusion.

 

"Gurhujhilljxzgrqqwa…" The creature gurgled followed by some deep clicking sounds that put Dean on edge.

 

"Look, if you're going to eat me I feel it's only right that I warn you I'm about ninety-five percent hard liquor and five percent self loathing so I ain't gonna taste good...oh, God, you don't understand me, you're gonna eat me and Sammy's gonna think I got drunk and fell off the Impala."

 

More clicking joined by a strange look as the creature sniffed at the air before it was crawling towards Dean with a disconcerting sucking sound as its many suction cups suckered around the ground below its mass of tentacles.

The sight would have been fascinating if Dean wasn't imagining his death by strange Octoman.

 

Dean scooted backwards until his back made contact with the smooth cave wall and turned his head away with screwed up eyes when the creature bent in to sniff enthusiastically at his throat - it made an odd, high-pitched, trill and Dean cracked open one of his eyes to peer at the face of the creature.

Rectangular pupils dilated and swallowed the bright, azure, iris' almost fully in what Dean would normally attribute to arousal in a human.

 

Curiously Dean took a tentative sniff in return and inhaled the scent of brine accompanied by an incredibly heady musk that made his mouth water and his heart race.

 

#  †

 

 Everything in Castiel was screaming at him to mate with this strange creature - it was an Omega and his Alpha  _ needed _ to breed it.

But the thing couldn't even understand him and though it appeared intelligent how could he know? If he mated with this creature and it wasn't sentient and couldn't understand him that would be rape.

 

The thing smelt heavenly though - sweet without being overbearing and thoroughly radiant.

 

Without the off helmet adorning its head Castiel could see the bright green of the creature's strange eyes with their round pupils growing larger as he peered closer.

The skin on it's uncovered face was a shade or two darker than Castiel's with brown dots marking it in places and a pink blush spreading across its cheekbones.

 

He didn't register one of his front limbs raising until he watched it caress the creature's face with a surreal kind of detachment.

The creature leant into the contact and let out a soft grunt sound that had Castiel's skin thrumming with electricity.

 

Castiel trailed the same limb along the creature's pink lower lip and watched as a wet tongue like his own darted out to taste the underside - he gasped and felt the rest of his limbs flexing and moving restlessly as green eyes stared into his own.

 

"I shouldn't…" Castiel groaned, his mating arm was restlessly curling and uncurling among his other limbs.

 

"Aaan, iunnO ot oar ayin ut amn ooo ell oood." The creature groaned in its deep and delicious tone, eyes burning into Castiel's own.

 

It was like it was replying...maybe it did understand but it couldn't grasp the language.

 

And surely if the creature smelled like  _ mate  _ that meant it was okay, any old random fish didn't smell like mate to him or anyone else he knew and Castiel had never met any other creature outside of his kin that had mates like his kin did.

As he thought more about it he remembered the tales elder members had told of other kindoms that looked different and figured this must be a member of one of those.

 

That would explain the similarities between them.

 

Castiel let his gaze slide from the other kin's face and down its slight but muscled chest with its sleek, black, skin bearing slight raised patterns like the freckles on the other kin's face.

It's torso narrowed at the middle and made the kin's hips look shapely as they branched into its split two limbs that started thick and firm before tapering down to the long fins at the ends.

 

A low sound resonated from the other kin and Castiel met it's gaze again, it looked amused and as he watched it licked at it's lips which prompted Castiel's limp to venture across the spit slick flesh.

 

#  †

 

 Dean would have to be blind to miss the signals and with slick seeping from his hole and a great smelling Alpha all up in his business it was impossible to resist giving out his own signals.

 

He was almost able to forget that this Alpha was part Octopus as the heated blue eyes drank him in like he was the most gorgeous man to ever live - he huffed out a laugh as the creature made its clicking sounds like it was excited by looking at his body.

 

Blue eyes fixed on his again and Dean wetted his drying lips quickly as he stared back, the tentacle that had been absently stroking his jaw slid along his bottom lip after his tongue and suddenly he had to taste it.

 

Dean sucked the tentacle into his mouth and felt it writhing around as the Alpha let out what sounded oddly close to a growl - a very,  _ very _ , happy growl.

 

The tentacle plundered his mouth and Dean let his jaw go slack as he tangled his tongue with the solid length, eager suckers pulled at his inner flesh and he let out a groan when he imagined what those suction cups would feel like in  _ other _ places.

 

And  _ fuck _ if that wasn't the hottest thing ever!

 

It was impossible now to ignore the boner that was straining to break free from the confines of his wetsuit and Dean fumbled for his zipper in a battle to relieve some of the pressure.

 

The Octo-Alpha's other tentacles were getting in on the action now, moving around Dean and roving across his body in waves with their sucking sounds echoing in the cave and driving Dean to insanity.

 

"Fuck, I need to get out of this thing!" Dean growled as he tore at his suit, the zipper gave and he essentially hulked out of the restricting fabric.

 

Hazy, blue, eyes widened marginally as the Octo-Alpha let out what sounded like a confused trill - one of its tentacles moved to slide the suit off of Dean's shoulders and Dean helped by pulling it off of his arms and peeling it down his waist.

 

The suckers of that same tentacle zeroed in on one of Dean's nipples and he bucked his hips involuntarily, his hard cock bumping against the space where Octo-Alpha's tentacles separated slightly drawing another growl as the Alpha wrapped a thick tentacle around Dean's waist.

 

He was going to have a lot of weird bruises and for some reason the thought of being marked by  _ his _ Alpha made his heart rate spike…

 

#  †

 

 It seemed the other kin had been wearing a second skin and although he knew that fact would have ordinarily freaked him out he couldn't dwell on that right now - not when the smell of Omega slick was filling the cave and he had a needy mass of bucking mate wrapped in his hold.

 

Castiel could feel a burn prickling under his skin as his mating arm pulsed with want, this was very new considering he'd never so much as thought of anyone as a mate before and his head was spinning as he nudged his most sensitive limb against the split of the Omega's two lower limbs.

 

With females of his species their openings were located underneath but he didn't know where this Omega's mating orifice was with the weird second skin in the way.

 

As if the other kin was reading his mind it wriggled it's hips out of the second skin and exposed the pink flesh beneath until the smell of slick had Castiel tightening his hold around it and rolling his mating arm against the Omega's squirming body.

 

A long third lower limb sprung free and the other kin hissed in what sounded like relief - Castiel looked at the reddened tip and watched intently in his lust filled haze as a pearly bead of liquid seeped free from a split at the end, the sight made his lower abdomen tighten and he lost no time stroking one of his limbs across the Omega's newly exposed limb which elicited a strong groan.

 

Castiel gripped the Omega tightly as he tipped him slightly and peeled the second skin until the other kin could kick it off, his fins fell away with it to reveal pale ends with tiny tentacles underneath that Castiel explored with one of his free limbs.

 

Tipping the Omega allowed him to find the source of the slick and he stared at the drenched space at the top of the three lower limbs while the Omega spread himself out where he was suspended in Castiel's hold.

 

Castiel gripped the underside where two thick and plump muscles were located separating the globes to reveal a puckered opening located behind two balls, it was pink and glistening enticingly.

 

He couldn't wait to explore it.

 

#  †

 

_ Yesyesyesyesyes _ Dean's mind chanted as one of the Octo-Alpha's many tentacles slid along the cleft of his ass and the suction cups pulled at the tingling flesh of his perineum towards the end of its lingering trail.

It felt so damn good to have that fucking tentacle stroking along his burning flesh, the cool length of it lessening the raging fire that had started consuming him.

 

He wasn't stupid, he knew his heat had been triggered and he knew if he didn't get that damn hectocotylus inside him soon he was going to combust.

 

"C'mon Alpha, mate me…" Dean begged, his body trembling with need.

 

The Alpha's eyes widened as he froze causing Dean to whine, "Maaate?" The Alpha repeated in an amazed tone like he couldn't believe what Dean had said.

 

Dean didn't register the fact that the Octo-Alpha knew the word mate, he just whined, "Yes, mate me, Alpha."

 

Blue eyes flashed at him as the Alpha clicked rapidly and circled Dean's rim with the tip of one tentacle causing Dean to buck wildly and practically sob.

The Alpha kept it's gaze on Dean's face as it smothered it's tentacle in slick and teased at the ring of muscle, pressing inwards with consistent pressure until the tip breached his tight hole .

 

Dean gulped and tipped his head back as his eyes rolled, cock twitching with another of the Alpha's tentacles wrapped firmly around it - a third tentacle slid along Dean's jaw and tipped his head to force his gaze back to the Alpha's.

 

The tentacle in his ass pushed deeper and began shallowly probing in and out with the suckers pulling at his rim making Dean's toes curl.

It wasn't in deep yet but it already felt  _ so  _ good that he was fighting the urge to cum - it seemed the Alpha knew this though, the tentacle around Dean's cock squeezed tight and held its position, acting like a cockring and driving Dean closer to the brink of absolute insanity.

 

Another push had the tentacle sliding impossible deep all at once and Dean let out a yelp of pleasure as white hot sparks shot up his spine - one of the suction cups was flexing around his prostate, massaging it in tandem as the tip of the tentacle nudged its way past his cervix and did a bizarre twisting movement as it drilled inwards.

 

This was by far the best sex Dean had ever had.

 

#  †

 

 Castiel had one of his limbs buried deep inside the Omega which was apparently very pleasurable if the Omega's panting and moans were anything to go by.

He had intended to stretch the other kin out but when his mate had started to show signs that the experience was extremely enjoyable Castiel had decided to linger on trying to make this last.

 

Now that the Omega's channel was feeling looser around Castiel's limb he felt confident enough to line his thicker mating arm up.

He didn't bother removing the first limb, he wanted his Omega stuffed full and stretched out nicely.

 

Castiel drew in a sharp breath as his mating arm breached the still tight entrance and felt his arousal reach new heights when his mate's eyes rolled for a second time.

 

The Omega's mouth was hanging open to show two rows of straight, blunt, teeth and the slick hole of his throat which Castiel hastened to stuff with one of his other limbs - he watched as his mate's eyes fluttered closed and felt his mating arm spasm inside his mate's slick hole when that warm mouth sucked around him.

 

"Good Omega." Castiel hummed as he slid his mating arm deeper.

 

His mate trembled in his hold and made delightful noises around his tentacle, green eyes opened halfway as he gazed at Castiel with reverence unlike anything he'd seen before.

The look had him melting against his Omega as he slipped his tentacle free from the plush lips and trailed a wet line down to his mate's chest to slide against a stuff nipple as he leant down and sealed their mouths together in an all consuming kiss.

 

His hold around his mate tightened while his tongue thrust into his mouth in time to the slow thrusts of his mating arm - he kept the tentacle that was inside his mate still and let his suckers apply pressure to the small nub that seemed to please his mate.

 

The kiss grew deeper and so did Castiel's thrusts, until he was hitting against something  _ very _ deep inside the Omega that he knew from his brother's mating seasons was where he needed to release his ejaculate to breed his mate.

He didn't know if the Omega would understand like he had with the word mate but he tried anyway, voice breathless as his words fanned out against his mate's swollen lips.

 

"Breed?" Castiel asked, eyes hooded as he gazed at his mate.

 

"Leaseeee, Alpha,  _ breed _ eeee." His mate said in a high whine.

 

"Claim?" His heart was pounding, not knowing if he would be able to handle rejection.

 

The Omega made a low, loud and drawn out sound of pleasure as the other kin's eyelids fluttered closed briefly.

 

"Claim. Breed. Alpha." His mate hissed, heat burning behind the green eyes.

 

Castiel moved one of his hands from his mate's shoulder up into his hair where he tangled his fingers in the short, light, strands and held tightly.

He thrust hard and fast into his mate as the other limb he had inside twisted and rippled, his mate was letting out increasingly loud sounds and gripping his shoulders tight enough to be painful.

 

He was pushing so deep now that the tip of his mating arm was plunging past some inner ring and he was panting breathlessly as he slid his mouth wetly down to the spot where his mate's throat joined his shoulder - he nosed at the spot where he'd leave his claiming bite and stroked his mate's rigid and leaking third limb in tandem to his thrusts.

 

Hot, white, liquid spilled out over his limb after a few strokes and his mate's eyes rolled back as his entire body pulled taut in Castiel's hold.

Powerful muscles rolled as he watched while his mate's breeding channel convulsed and massaged his mating arm from deep within.

 

It was almost impossible to move inside his mate now that he was pulsing and seizing around him with a steely grip and Castiel came deep inside with a shout of pleasure - the instant his climax struck Castiel bent and sank his sharp teeth into his mate's throat feeling the gush of warm liquid that rushed into his mouth.

 

#  †

 

 Dean must have blacked out because when he became aware of himself again  _ his _ Alpha was gently licking at the fresh claim on Dean's throat and that thick tentacle was steadily pumping more and more of the Octo-Alpha's cum into him.

_ Fuck _ , it felt so good and when he looked down at his stomach it was bulging with his mate's seed.

 

He clenched around the Alpha and listened to the sharp intake of breath as another flood of cum spurted out like a super soaker being shot at full blast.

 

Dean was still hard and his Alpha's tentacle was slowly pumping his length, slick with his own cum - he moaned at the sight which caused his mate to look at him with a blissed out smile.

 

"Omega." His mate said slowly.

 

"Yes, your Omega," Dean hummed in response as he lowered a hand to stroke at his full stomach, "When are we starting round two?"

 

His mate gave a gummy smile that made his nose scrunch up and clicked out his response, they were going to have to work out a way to communicate properly.

  
  
  
  


**Author's Note:**

> This was a one shot piece, thank you for reading and I hope you liked it.  
> As always, feedback is greatly appreciated xoxo


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